In [1]:

```
import math
# Variables
r_o = 2.8 #interatomic distance in Å
R_o = 2.8*10**(-10);#interatomic distance in m
u_o = 8.; #released energy in eV
e = 1.6*10**(-19); #charge of electron in C
U_o = 8.*e #released energy in Joule
# Calculation
A = (5./4)*U_o*(R_o**2); #proportionality constant for attraction in J-m2
B = A*(R_o**8)/5; #proportionality constant for repulsion in J-m2
r_c = (110*B/(6*A))**(1./8); #interatomic distance at which the dissociation occurs in m
F = -(2/r_c**3)*(A-5*B/(r_c**8)); #the force required to dissociate the molecule in N
# Results
print 'proportionality constant for attraction = %.2e J-m2'%A
print 'proportionality constant for repulsion = %.2e J-m2'%B
print 'interatomic distance at which the dissociation occurs = %.2e m'%r_c
print 'the force required to dissociate the molecule = %.2e N'%F
```

In [2]:

```
import math
# Variables
r_o = 3.14; #nearest neighbour equilibrium distance in Å
R_o = 3.14*10**(-10); #nearest neighbour equilibrium distance in m
K = 5.747*10**(-11); #compressibility of KCl in m2/N
M = 1.748; #Madelung constant
pi = 22./7;
# Calculation
E_o = 8.854*10**(-12);
q = 1.6*10**(-19); #electron charge
n = 1+18*(R_o**4)*4*pi*E_o/(K*M*q**2);
# Results
print 'repulsive exponent n = %.1f'%n
```

In [4]:

```
import math
# Variables
F_1 = 3.02*10**(-9); #force of attraction b/w ions of Na+ and Cl-
Z_1 = +1;
Z_2 = -1;
e = 1.6*10**(-19);
E_o = 8.854*10**-12;
pi = 22./7;
r_Na = 0.95; #ionic radius of Na+ ion
# Calculation
r = (-Z_1*Z_2*e**2/(4*pi*E_o*F_1))**(1./2); #Radius of ion in meter
R = r/10**(-10); #Radius of ion in Angstrom
r_Cl = (R-r_Na); #Radius of Cl- ion in Angstrom
# Results
print 'Ionic Radius of Cl- ion in = %.2f Angstrom'%r_Cl
```

In [5]:

```
import math
# Variables
Z_1 = +2;
Z_2 = -2;
r_Mg = 0.65; #radius of Mg++ ion
r_S = 1.84; #radius of S-- ion
r = r_Mg+r_S; #net radius(in Angstrom)
# Calculation
R = r*10**(-10); #net radius(in meter)
e = 1.6*10**(-19);
E_o = 8.854*10**-12;
pi = 22./7;
F = -Z_1*Z_2*e**2/(4*pi*E_o*R**2); #force of attraction between ions(in Newton)
# Results
print 'force of attraction between ions in = %.1e Newton'%F
```

In [7]:

```
import math
# Variables
#Na atom requires +5.14 eV of energy. When this electron is transferred to a vacant position,it gives back –4.02 eV of energy
E_1 = +5.14; #in eV
E_2 = -4.02; #in eV
# Calculation
NET_energy = E_1+E_2; #in eV
# Results
print 'Net spent energy in whole process in = %.2f eV'%NET_energy
```

In [8]:

```
import math
# Variables
Enthalpy = 6.02; #enthalpy of fusion of ice is 6.02 kJ/mol
E_h = 20.5; #Hydrogen bond energy (in kJ/mol)
#There are two moles of hydrogen bonds per mole of H2O in ice.
# Calculation
H_b = Enthalpy/(2*E_h); #the fraction of hydrogen bonds that are broken when ice melts
# Results
print 'fraction of hydrogen bonds that are broken when ice melts = %.2f'%H_b
```